▲ Quick answer

Root servers are the name servers at the very top of the DNS. They answer the first step of a lookup — “which servers run this top-level domain?” — pointing resolvers toward the right registry. There are 13 named identities (A–M), each backed by many servers worldwide through anycast, and coordinated by IANA.

Almost every DNS lookup, in principle, begins at the root. Yet the root is one of the most misunderstood parts of the internet — people picture 13 lonely machines holding the whole web together. The reality is far more robust and a lot more interesting.

What are root servers?

Root servers are the authoritative servers for the root zone — the unnamed zone at the apex of the DNS, written as a silent trailing dot in example.com.. They do not store information about individual websites. Their single job is to know which servers are responsible for each TLD, so they can hand a resolver off in the right direction.

Root name server

A DNS server at the top of the namespace that answers queries about the root zone, directing resolvers to the name servers for each TLD. Thirteen named identities (A–M) front thousands of anycast instances.

Why are there exactly 13?

The famous number 13 is a historical artifact. In the early DNS, a single response packet could only carry a limited amount of data, which capped how many root server addresses could be listed at once — that practical limit settled at 13. The names run a.root-servers.net through m.root-servers.net.

Rather than break compatibility by adding a 14th name, engineers found a better way to grow: scale each of the 13 identities into many physical servers.

How 13 names became thousands of servers

The trick is anycast routing. With anycast, the same IP address is announced from many locations around the world at once; the network simply delivers your query to the nearest instance. So when you query “A root” from London, you reach a London-area copy; from Tokyo, a Tokyo-area copy. Each of the 13 identities is fronted by dozens or hundreds of these instances — well over a thousand in total — giving the root enormous capacity and resilience while keeping just 13 names.

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13 identities, not 13 machines

This is the key insight: the “13 root servers” are 13 addresses, each served by a large, globally distributed fleet. The system is designed so that no single machine — or even many machines — is a point of failure.

Their role in a lookup

Where do root servers fit in resolving a name? They are step one:

  1. A resolver, needing to find example.com, asks a root server: “Where are the .com servers?”
  2. The root replies with the .com registry’s name servers (it does not know example.com itself).
  3. The resolver then asks the .com servers, which point to example.com’s authoritative name servers.
  4. Those return the final answer.

In practice, resolvers cache the root’s answers heavily, so they rarely need to ask the root again for the same TLD. See the full walkthrough in how domain name resolution works.

Who runs the root servers?

The 13 identities are operated by 12 independent organizations — including universities, technology companies, non-profits and bodies connected to internet governance. They serve the same root zone data, the contents of which are managed by IANA (an ICANN function) and published as the authoritative root. No single operator controls the root; the diversity is deliberate.

Why root servers matter

You will never configure a root server, but they explain something fundamental: how a lookup starts, and why the internet’s naming system is so dependable. The root’s combination of a tiny, stable set of names with a massive, distributed backing is a model of resilient design — and it is the reason the phrase “the internet is held together by 13 servers” is more myth than fact.

★ Key takeaways

  • Root servers sit at the top of DNS and direct resolvers to the right TLD servers.
  • There are 13 named identities (A–M) — identities, not single machines.
  • Anycast backs each identity with many instances worldwide (1,000+ total).
  • They are run by 12 organizations; the root zone is coordinated by IANA.

Frequently asked questions

How many root servers are there?

There are 13 named root server identities, labeled A through M (for example a.root-servers.net). Each identity is not a single machine but a cluster of many servers spread worldwide — well over a thousand instances in total — using anycast routing.

Why are there only 13 root servers?

The number 13 dates to early technical limits on how many name server addresses fit in a single DNS response packet. Rather than add more named identities, the system scaled within each of the 13 using anycast, so 13 names now front thousands of physical servers.

What do root servers actually do?

Root servers answer the first question in a lookup: “which servers are authoritative for this TLD?” They do not know individual domains — they direct resolvers to the right TLD registry servers, which then point to the domain’s own name servers.

Who controls the root servers?

The 13 root server identities are operated by 12 independent organizations — a mix of universities, companies, non-profits and government-related bodies. The contents of the root zone they serve are coordinated by IANA (part of ICANN).

Could the internet break if root servers went down?

It is extremely resilient. With 13 identities backed by thousands of anycast instances across the globe, plus heavy caching by resolvers, the root is designed so that losing many instances causes little or no disruption. A total, simultaneous failure is highly improbable.

Sources & further reading